1. Technical Field of the Invention
The present invention relates to an apparatus and a method for fuelizing inflammable waste, and more particularly to an apparatus and the like used for utilizing wastes containing inflammable material such as plastics.
2. Description of the Related Art
It has been used techniques of grinding inflammable wastes such as waste plastics to less or equal to some degree of sizes and fuelizing the ground inflammable wastes. When using such singly ground plastics as a substitute fuel for combustion device using pulverized coal, heavy oil and so on, however, the ground plastics are liable to cause landing combustion, consequently deteriorating the quality of burnt product. Then, in order to prevent the landing combustion, the grinding can be more finely carried out. However, in such a case, excessive grinding may occur, which causes remarkable enhancement of grinding cost especially in plastics that are difficult to grind.
Therefore, the present applicant proposed a method for fuelizing plastics, as described in Patent document 1, in accordance with knowledges that crushed plastics blown from a cement kiln front stay in the cement kiln for approximately 2 seconds at approximately 800 to 1600°, and burn up time of the crushed plastics varies with weight and surface area thereof so that plastics with larger surface area are burnt for a shorter burn up time, and so on. In this method, plastics are crushed to be 200 cm2/g or more in specific surface area as well as 0.01 g or more and 0.1 g or less in weight, and the crushed plastics are burnt in a combustion furnace of 800° or more, which allows the crushed plastics to completely be burnt within a stay time in the cement kiln space on the whole by regulating its shape factor even though grinding or breakage is stopped to a specific weight, resulting in burnt product with good property.
On the other hand, in order to obtain crushed plastics used for burning in combustion furnaces or the like, variety of crushers are used, however, in consideration of operational troubles such as breakage of rotary blades and others of the crushers and clogging of screens, in Patent document 2 is proposed a crushing device that uses a one-shaft-rotor-type rotary crusher, in which rotary blades and fixed blades disposed in the crusher crush waste plastics, and crushed waste plastics are discharged through a screen, and the crushed waste plastics are discharged with vertically sucked air in the crusher while rotating the rotary blades at low velocity between 60 rpm and 150 rpm, and so on.
Further, to the inflammable waste are mixed non-ferrous foreign matters such as sands, stones, glasses, copper and aluminum, and iron-based foreign matters, which causes fluctuation of calorific value when burnt in a burner or the like, so that the foreign matters should be removed in advance. In addition, these foreign matters may cause the breakage of crushing blades at crushing processing, which causes increase in maintenance cost and reduction in operational rate. Therefore, in conventional methods of fuelizing inflammable waste, brought-into inflammable wastes were primarily crushed as well as foreign matters such as metals were removed from the primarily crushed objects, after that, they were secondarily crushed so as to be used as a fuelized matters.
In this case, in order to remove foreign matters such as metals, a foreign matter removing device as shown in FIG. 5 is used. The foreign matter removing device 24 is composed of a magnetic ore dressing machine 22 mounted above a vibrating conveyor 21, and a screen 23 disposed downstream of the magnetic ore dressing machine 22, and from crushed objects of flammable wastes such as plastics, sponges, fibers, rubbers, wood materials and construction-based wastes are removed iron-based foreign matters M by the magnetic ore dressing machine 22, and non-ferrous foreign matters I such as sands, stones, glasses, copper and aluminum are removed through the screen 23.
Then, fuelized matters obtained by secondary crushing after removing foreign matters were transported to a tank mounted near a front portion of a rotary kiln and were stored therein, and appropriately, the fuelized matters were supplied to a burner and were blown into the rotary kiln while required amount being measured.    Patent document 1: Japanese Patent Publication 2001-181658 gazette    Patent document 2: Japanese Patent Publication 2007-190481 gazette